The governing board of the society is its board of trustees which consists of officers, trustees and ex-officio members. The elective officers of the society shall be president, vice president for eastern Washington, vice president for western Washington, and treasurer. The director of the society serves as the secretary to the board of trustees. The trustees number not less than twenty and no more than thirty. The governor, secretary of state, superintendent of public instruction and legislators representing each of the four caucuses of the state legislature are ex officio voting members of the board of trustees.